CBSE 11th Standard Physics Subject Waves Ncert Exemplar 5 Mark Questions With Solution 2021
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CBSE 11th Standard Physics Subject Waves Ncert Exemplar 5 Mark Questions With Solution 2021
11th Standard CBSE
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Reg.No. :
Physics
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For the harmonic travelling wave \(y=2\cos { 2\pi } \left( 10t-0.0080x+3.5 \right) \), where, x and y are in cm and t is in second. What is the phase difference between the oscillatory motion at two points separated by a distance of What is the phase difference between the oscillation of a particle located at x=100 cm, at t=Ts and t = 5s?
(a) -
In the given progressive wave, Where, y and x are in m,t is in seconds. What is the wavelength?
(a) -
In the given progressive wave
y=5sin(100πt−0.4πx) where y and x are in m,t is in s.
A: What is the amplitude and wavelength?
B: What is the frequency and wave velocity? (Wavelength is 5 m)
C: What is the particle velocity amplitude?(a)
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CBSE 11th Standard Physics Subject Waves Ncert Exemplar 5 Mark Questions With Solution 2021 Answer Keys
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Given equation is \(y=2\cos { 2\pi } \left( 10t-0.0080x+3.5 \right) \)
Comparing with standard equation,
\(y=2\cos { 2\pi } \left( 10t-0.0080x+3.5 \right) \)
\(y=a\cos { \left( \omega t-kx+\phi \right) } \)
\( a=2cm,\omega =\frac { 2\pi }{ T } =20\pi ,\ T=0.1s\)
\( k=\frac { 2\pi }{ \lambda } =0.008\times 2\pi \Rightarrow \lambda =\frac { 2\pi }{ 2\pi \times 0.008 } =1.25m\)
\(\\ \phi =2\pi \times 3.5=7\pi rad\)
\(At\ t=T;\phi =\frac { 2\pi }{ T } =\frac { 2\pi }{ 0.1 } =20\pi rad\)
\(\\ and\ at\ t=5s;{ \phi }^{ ' }=\frac { 2\pi }{ 0.1 } \times 5.100\pi rad\)
\(\therefore phase\ difference\ { \phi }^{ ' }-\ \phi =100\pi rad-20\pi rad=8020\pi rad\). -
\(\omega =\frac { 2\pi }{ T } =100\pi \)
\( K=\frac { 2\pi }{ \lambda } =0.4\pi \Rightarrow \lambda =\frac { 2 }{ 0.4 } =\frac { 20 }{ 4 } =5m\) -
A: Find amplitude of the given wave.
Given, progressive wave,
y=5sin(100πt−0.4πx)
So, amplitude of the given wave,
a=5 m
Find wavelength of the given wave.
Since we know
k=2π/λ
According to the given wave equation,
Angular wavenumber, k=0.4π
2π/λ=0.4π
λ=20/4=5 m
Final answer: 5m;5m
B: Find frequency of the wave
Given, wave equation,
y=5sin(100πt−0.4πx)
From the given waveequation, angular frequency,
ω=100π
Since ω=2πf
So,frequency,
f=ω2/π
\(\omega =2\pi v=100\pi v=50Hz\)
f=100π/2π=50 Hz
Find wave velocity of the wave.
Given, wavelength of the wave,
λ=5m
Wave velocity, v=fλ
v=50×5=250m/s
Final Answer: 50 Hz;250m/s
C: Particle velocity: Particle velocity is the velocity with which particles vibrate during the wave propagation.
Given, wave equation,
y=5sin(100πt−0.4πx)
Velocity of the particle by, \(\frac{\partial_{\mathrm{y}}}{\partial_{\mathrm{t}}}=\frac{\partial}{\partial_{\mathrm{t}}}(5 \sin (100 \pi \mathrm{t}-0.4 \pi \mathrm{t})) \)
\( \frac{\partial_y}{\partial_t}=500 \pi \cos (100 \pi t-0.4 \pi x)\)
So, particle velocity amplitude = \(500 \pi \mathrm{m} / \mathrm{s}\)
Final Answer: \(500 \pi \mathrm{m} / \mathrm{s}\)